1. Field of the Invention
The present invention relates to optical processors, and more particularly, to optical target recognizer systems incorporating a multiple target correlator. The multiple target correlator utilizes multiple matched filters, two for each individual target or object, recorded at a predetermined unique angular difference on a single plate and provides a method for interrogating these multiple target matched filters with a particular scene of interest.
2. Discussion of the Prior Art
In today's "high-tech" manufacturing environment, fabrication trends have been toward closer tolerances and higher complexity, thereby leading to highly labor intensive manufacturing processes. The introduction of automated assembly systems, such as robots, into the factory has been slow in coming due to today's lower production rates. A cost effective approach or solution to this problem is the use of flexible manufacturing systems, utilizing robotics, which are capable of working on a variety of assemblies having similar construction. One of the major limitations associated with the use of robotic systems is the identification of the various components used to manufacture a given product. Early robotic vision systems incorporated a main frame computer which would decompose a particular image of each viewed part into a series of lines and arcs which were used to locate and identify the selected part.
To meet the increasing demand placed upon robotic systems, robotic vision subsystems with increased memory and performance were designed. These vision subsystems were designed to be smaller in size and lower in cost while providing higher acquisition and processing rates for higher rates of production. In order to provide this, the vision subsystems incorporated optical target recognizer systems employing optical correlation techniques.
Present optical target recognizer systems can detect, locate and track a specific target for various target orientations. The optical target recognizer system can be designed to accept a real time image of a scene in which a target of interest may or may not be present. The input image is converted into an electrical signal which in turn is input to a spatial light modulator. The spatial light modulator serves to store an image of the real time input and acts like an optical transparency impressing the image onto a laser beam in the form of amplitude and/or phase modulation. The image modulated laser beam is then Fourier transformed and directed to an optical matched filter. The matched filter contains previously recorded Fourier transform holograms of targets of interest. The output of the matched filter is Fourier transformed again to achieve an inverse Fourier transform. The result of this inverse Fourier transforming step results in an autocorrelation signal if there is a match between the input image and the recording on the matched filter, and a cross-correlation signal if there is no match. While this operation for a specific target functions extremely well, it does not provide a means for unambiguously detecting, identifying, locating and determining the orientation of each target in a scene including multiple targets.
Manufacturing processes that require multiple parts require robotic systems that can not only detect the various parts, but also differentiate between the various parts. The basic problem is, given a multiple of input objects and a corresponding multiple of matched filters, how is one to determine which correlation spot (autocorrelation) belongs to which object and how is the orientation of each object to be determined. With the present state of the art, to acquire multiple objects, a series of matched filters and a transport mechanism are needed to eliminate the ambiguity. Alternative methods considered involve the use of multiple recording techniques with holographic or optical tags to differentiate between objects and determine their orientation. As of the present date, there has been little success on how these prior art approaches might be effectively implemented.